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Method for extracting alumina from coal ash through wet process

A technology for fly ash and alumina, applied in the removal of alumina/aluminum hydroxide, solid waste, etc., can solve the problems of low content of harmful impurities in residues, high alumina dissolution rate, corrosion of acid process equipment, etc. Energy consumption, simplified production process, reduced corrosive effect

Active Publication Date: 2012-05-30
INST OF PROCESS ENG CHINESE ACAD OF SCI
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  • Abstract
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Problems solved by technology

[0005] The purpose of the present invention is to overcome the defects of high energy consumption, difficult operation, serious corrosion of acid process equipment, and hidden danger of secondary pollution caused by high temperature operation when processing fly ash by high temperature sintering method, and provide a low temperature wet process in alkaline medium A new method for extracting alumina from high-alumina fly ash, with high alumina dissolution rate, small amount of residue, and low content of harmful impurities in the residue, easy to realize resource utilization of waste

Method used

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  • Method for extracting alumina from coal ash through wet process

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Effect test

Embodiment 1

[0025] The aluminum oxide in the fly ash is recovered by the low-temperature wet method provided by the present invention. Taking the fly ash in a certain place in Inner Mongolia as an example, the percentage content of the main element oxides of the fly ash is as follows:

[0026] al 2 o 3 SiO 2 Fe 2 o 3 CaO TiO 2 Na 2 O H 2 O burn reduction A / S

[0027] 41.41 39.54 2.40 3.67 1.38 0.21 6.1 2.81 1.05

[0028] Its recycling steps are:

[0029] The fly ash and the mass percentage are 50% NaOH solution mixed and placed in the reactor, the alkali solution and the fly ash mass ratio are 10.3: 1, the calcium oxide addition is 50% of the fly ash quality, and the temperature is raised to 260°C, reacted at 1.6MPa for 1 hour to obtain a mixed reaction product of alkali solution containing sodium aluminate and dealuminated slag. After the mixed reaction product was cooled to 100°C, it was filtered to obtain an alkali solution containing sodium aluminate and dealuminated sla...

Embodiment 2

[0033] The fly ash of embodiment 1 is mixed with the crystalline mother liquor in embodiment 1 and then placed in the reactor, the mass ratio of mother liquor and fly ash is 12.98: 1, and the calcium oxide addition is 35% of the fly ash quality, Raise the temperature to 300°C and react for 2 hours to obtain a mixed reaction product containing lye, sodium aluminate and dealuminated slag. After the mixed reaction product is cooled to 100°C, perform suction filtration to separate and obtain an alkali solution containing sodium aluminate and dealuminated slag. Slag, A / S=0.02 in the dealuminated slag at this time (A is the mass percentage of alumina, S is the mass percentage of silicon oxide), and the recovery rate of alumina in the fly ash is 98%.

[0034] Put the obtained sodium aluminate-containing alkali solution (filtered mother liquor) into a crystallization reactor, crystallize at 100°C for 10 hours with the addition of 8% seed crystals, and increase the caustic ratio of the ...

Embodiment 3

[0037] The fly ash of Example 1 is mixed with 30% NaOH solution by mass percentage and then placed in the reactor. The mass ratio of the alkali solution to the fly ash is 17.45:1, and the amount of calcium oxide added is 60% of the fly ash quality. %, heat up to 300°C, and react at 6.2MPa for 0.5h to obtain a mixed reaction product of lye containing sodium aluminate and dealuminated slag. After the mixed reaction product is cooled to 100°C, perform suction filtration to obtain aluminum-containing acid Sodium alkali solution and dealuminated slag, A / S=0.35 (A is the mass percentage of alumina, S is the mass percentage of silicon oxide) in the dealuminated slag at this time, the recovery rate of alumina in the fly ash is 66.67%.

[0038] Put the obtained sodium aluminate-containing alkali solution (filtered mother liquor) into a crystallization reactor, crystallize at 60°C for 3 hours with the addition of 5% seed crystals, and then increase the caustic ratio of the filtered cryst...

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Abstract

The invention provides a method for extracting alumina from coal ash through a wet process. The method comprises the following steps: 1, mixing the coal ash, calcium oxide and an alkaline solution, reacting, carrying out flash evaporation, and filtering to obtain an alkaline solution containing sodium aluminate and aluminum removed slag; 2, cooling and crystallizing the alkaline solution obtained in step 1 to obtain a coarse hydrated sodium aluminate crystal and a crystallization mother solution; 3, circulatingly applying the crystallization mother solution obtained in step 2 to a leaching reaction, dissolving the coarse hydrated sodium aluminate crystal with water or a diluted alkaline solution, carrying out silicon removal and seed decomposition to obtain aluminum hydroxide, and calcining aluminum hydroxide to obtain alumina; 4, evaporating the seed-decomposed mother solution, and mixing the evaporated seed-decomposed mother solution with the alkaline solution obtained in the step 1; and 5, carrying out hydrolysis sodium removal on the aluminum removed slag obtained in the step 1 in the diluted alkaline solution, filter-separating, and carrying out multistage countercurrent washing on the sodium removed slag. According to the method, the dissolving-out temperature and the dissolving-out pressure are low, the dissolving-out rate of alumina can reach above 90%, and the content of sodium oxide in the sodium removed slag is less than 1%.

Description

technical field [0001] A method for extracting alumina from fly ash, in particular to a method for recovering alumina from fly ash by wet method. Background technique [0002] At present, the production of alumina mainly uses bauxite as raw material to produce by alkaline method, including Bayer method, sintering method and combined method. my country has become a large alumina producer, but the bauxite resource guarantee is low, and the resource problem has become the main bottleneck for the sustainable development of my country's alumina industry. [0003] Fly ash is one of the solid wastes produced after coal combustion, and the accumulated stockpile has reached 2 billion tons. The development and utilization of fly ash to produce alumina is undoubtedly of great significance to solve the shortage of bauxite resources and environmental pollution caused by coal burning in our country. [0004] There are a series of patent applications for the technology of extracting alum...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01F7/02B09B3/00
Inventor 马淑花杨权成郑诗礼张懿
Owner INST OF PROCESS ENG CHINESE ACAD OF SCI
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